Prestressed concrete hull and method of making the same



June 13, 1967 ALFRED A, YEE 3,324,814

PRESTRESSED CONCRETE HULL AND METHOD OF MAKING THE SAME Filed March 16, 1965 4 Sheets-Sheet 1 Alfred A. Yee

INVENTOR.

June 13, 1967 ALFRED A. YEE 3,324,314

PRESTRESSED CONCRETE HULL AND METHOD OF MAKING THE SAME Filed March 16, 1965 4 Sheets-Sheet 2 Fig. 4 V

Alfred A. m

INVENTOR.

June 13, 1967 ALFRED A. YEE

PHESTRESSED CONCRETE HULL AND METHOD OF MAKING THE SAME 4 Sheets-Sheet Filed March 16, 1965 R. m e m M m M o A A 1 H m L f f m Q. Y B m vw k L N\ mm wk Wk ww ww 3v QM NW QM June 13, 1967 ALFRED A. YEE 3,324,814 I PRESTRESSED CONCRETE HULL AND METHOD OF MAKING THE SAME Filed March 16, 1965 4 Sheets-Sheet 4 Patented June 13, 1957 3,324,314 FREE RESSED (IGNCRETE H LL AND METHGD (3F lVIAKZN-G HE 8AME Alfred A. Yee, 3169 Alilra Ava, Honolulu, Hawaii 6817 Filed Mar. 16, 1965, Eer. No. 449,9?8 3 Cimms. (Cl. 114-5) This invention relates to a novel and useful prestressed concrete hull and the method of making the same. Basically, the prestressed concrete hull of the instant invention consists of a main framework including a plurality of longitudinally spaced and transversely extending upright open frame-like steel or reinforced concrete rib sections which are spaced uniformly along the longitudinal axis of the hull and which are interconnected by means of a plurality of longitudinally extending structural members.

After this frame has been formed, a plurality of longitudinally extending prestressing steel tendons, which may consist of single strands, groups of strands or high tensile rods or wires, are disposed adjacent the outer surface of the frame and spaced circumferentially about the girth thereof. Thereafter, inner and outer forms are erected sandwiching the reinforcing rods or tendons therebetween in spaced relation relative thereto and the steel tendons are then placed under considerable tension. Thereafter, the desired cementitious material is poured between the inner and outer forms with the steel tendons and other reinforcing steel rods embedded therein. As soon as the cementi iious material has thoroughly hardened, the prestressing steel tendons are relieved of their tension.

Inasmuch as the prestressing steel tendons can only be placed under considerable tension at a reasonable cost if they are straight, the concrete hull of the instant invention is constructed of a long center section including longitudinally straight sides and bottom surfaces and two relatively short opposite end bow and stern sections.

The longitudinally extending prestressing steel tendons utilized are of a length greater than the length of the desired completed concrete hull and project considerably outwardly beyond the opposite ends of the inner and outer forms erected about the framework during the pouring and har ening of the cementitious material. After the cementitious mate ial has hardened and the prestressed steel tendons are relieved of their tension, the extended end portions of the tendons projecting outwardly beyond the opposite ends of the completed center section of the concrete hull are bent into bow and stern section skeleton frames. Thereafter, inner and outer forms are erected sandwiching the bow and stern skeleton frames therebetween in spaced relation thereto and additional cementitious material is poured between the forms sandwiching the skeleton frames therebetween with the latter and other reinforcing steel embedded therein. After the cenentitious material of the bow and stern sections has thorougly hardened, the bow and stern inner and outer forms are removed leaving the completed prestressed concrete hull desired.

If it is desired to form individual compartments within the resultant hull assembly, suitable bulkheads may be erected adjacent to or within selected rib sections in order to form individual cargo receiving compartments spaced longitudinally of the hull. Still further, in order to form a tight seal between the center longitudinally straight section and the bow and stern sections of the hull, the opposite end faces of the center section have a suitable bonding and sealing compound such as epoxy applied thereto just prior to the pouring of the cementitious material in the inner and outer forms of the bow and stern sections of the hull.

The main object of this invention is to provide a prestressed concrete hull constructed in a manner such that the prestressed cementitious portions thereof will inherently resist flexing of any external forces applied thereto thereon such as by the buoyant force of the hull acting upon cargo supported therein or ocean waves. The cementitious portions of the hull being under a prestressed compression condition will also provide a construction having greater imperviousness against water penetration.

Another very important object of this invention, in accordance with the immediately preceding object, is to provide a method of manufacturing a prestressed cementitious hull which will enable the hull to be readily produced at a minimum of cost.

Still another object of this invention is to provide a prestressed concrete hull construction including a center section having substantially longitudinally straight hull portions whereby straight and longitudinally extending prestressing tendons may be used in order that such tendons may be readily placed under great tension during the construction of the center section of the hull with the latter initially defining an open-ended partial hull construction and subsequently closed at its opposite ends by the addition of bow and stern sections thereto. It is to be noted that if the configuration of the hull was such that longitudinal tendons embedded therein had to be curved, such tendons could not be readily tensioned nor could they be tensioned the same degree.

A final object of this invention to be specifically enumerated herein is to provide a prestressed cemeutitious hull which will conform to conventional forms of manufacture, be of simple construction and reasonably light in weight so as to provide a hull that will be economically feasible, long lasting and have a relatively large weight carrying capacity.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a perspective view of the completed prestressed concrete hull assembly of the instant invention:

FIGURE 2 is an enlarged transverse vertical and diagrammatic sectional view illustratin the structural features of one form of transverse rib section of the hull;

FIGURE 3 is an enlarged fragmentary transverse vertical sectional view similar to that of FIGURE 2 but on a larger scale;

FIGURE 4 is an enlarged transverse vertical sectional view similar to that of FIGURE 2 but illustrating a modified form of full decked hull construction and a modified form of rib section used in conjunction therewith;

FIGURE 5 is a fragmentary exploded perspective view of a portion of the structural frame of the hull;

FIGURE 6 is a diagrammatical side elevational view illustrating one of the initial steps-in the method of construct-ing the hull of the instant invention, which step includes the erection and pretensioning of the longitudinal reinforcing tendons to ultimately be embedded in the poured cementitious skin of the hull;

FIGURE 7 is a vertical transverse diagrammatical sectional view on an enlarged scale and taken substantially upon the planeindicated by section line 77 of FIG- URE 6;

FIGURE 8 is a perspective View of the completed center section of the hull having bulkheads erected therein and the ends of the longitudinal reinforcing tendons projecting from the opposite ends of the center section of U the hull bent so as to form the skeleton frames of the bow and stern sections of the hull.

Referring now more specifically to the drawings the numeral 10 generally designates the hull construction of the instant invention which may be seen in its completed form illustrated in FIGURE 1 and including a center section generally referred to by the reference numeral 12, a bow section generally referred to by the reference numeral 14 and a stern section generally referred to by the reference numeral 16.

The hull construction 10 is of the partially open desktype defining an accessible hold for receiving cargo to be transported. The bow section includes a full deck portion 18 in addition to its opposite sides and bottom and the stern section also includes a full deck portion 20. The center section 12 includes opposite side partial deck sections 22 and 24 between whose adjacent longitudinal edge portions a cargo receiving hold 26 is defined. In addition, the hull 10 includes a plurality of longitudinally spaced and transversely extending open frame-like rib sections generally referred to by the reference numeral 28, see FIGURE 5, which may have suitable partition or bulkhead assemblies generally referred to by the reference numerals 30 secured thereon or adjacent thereto in order to form individual cargo receiving compartments 32 within the hull 10.

With attention now invited more particularly to FIG- URES 3 and of the drawings it may be seen that each of the framelike rib sections 28 includes a pair of outer upstanding opposite wall frame members 34 between whose lower ends a lower generally horizontally disposed and transversely extending frame bottom member 36 is secured. In addition, each of the rib sections 28 includes a pair of inwardly directed upper transversely extending frame deck members 38 which project inwardly from the upper ends of the corresponding wall frame members 34. The inner ends of corresponding upper transversely extending frame deck members 38 are interconnected by means of upper longitudinally extending frame deck members 40 and a pair of longitudinally extending keelsons 42 interconnect the transverse bottom fram members 36 on opposite sides of the longitudinal center line of the hull 10. Still further, a plurality of vertical stanchions 44 interconnect the upper longitudinally extending frame deck members 40 and the keelsons 42 at a point spaced longitudinally therealong and at the intersections of the upper longitudinal frame deck members 40 and the keelsons 42 with the rib sections 28. The partitions or bulkhead forming assemblies 30 may be constructed of metal plates 46 reinformed as at 48 and secured within the hull adjacent or to the rib sections 28 in any convenient manner. In addition, the bulkhead forming assemblies 30 may also be constructed of reinforced concrete panels.

With attention now invited to FIGURE 4 of the drawings there will be seen a modified form of hull 10 including frame-like rib sections generally referred to by the reference numeral 28' which include upstanding opposite wall frame members 34 and lower transversely extending frame bottom members 36' corresponding to the counterparts of the hull 10. The hull 10' is very similar to the hull 10 with the exception that its center section is of the full deck type in that the upper transversely extending deck frame members 38' thereof extend the entire distance between the upper ends of the upstanding opposite Wall frame members 34'. If it is desired, the hull 10' may include longitudinally extending keelsons 42 and upper longitudinally extending deck members 40 also corresponding to the counterparts of the hull 10. However, the rib sections 28' may be of considerably lighter construction than the rib sections 28 inasmuch as each rib section 28 is cross-braced by means of truss-like structural members such as cross-braces 50 and 52.

With attention now directed more specifically to FIG- URES 6-8 of the drawings it may be seen that the hull construction 10 may be erected by erecting a plurality of longitudinally extending steel tendons 54 in a manner such that they are spaced circumferentially about the girth of the center hull section 12 to be constructed. Each of the tendons 54 is placed under great tension and anchored to suitable anchor assemblies 56 of similar and any suitable construction and supported against movement relative to each other. Then, the supporting frame of the hull construction 10 including the rib sections 28 and various interconnecting structural members 40 and 42 may be erected inwardly of the tendons 54 to complete the skeleton framework of the hull 10. As an alternative, the frame comprising the rib sections 28 and the interconnecting longitudinal bracing members 40 and 42 may be first erected between the anchors or supports 56 and the steel tendons 54 may then be erected about the completed frame.

It is to be noted that any suitable supporting structure (not shown) may be utilized for supporting the frame of a hull construction 10 in the desired position fixed relative to the pretensioned steel tendons 54. Further, any suitable means (not shown) may be utilized to place the tendons 54 under tension, the preferred method involving the steps of individually tensioning each tendon 54.

After the skeleton framework has been erected, mild steel rods 58 may be passed about the girth of the framework and have their opposite ends secured to any suitable structural members of the longitudinally extending combing assemblies 60 extending longitudinally of the inner edge portions of the partial deck sections 22 and 24, see FIGURES 3 and 7.

If it is desired, the mild steel rods 58 may be utilized in two sets of rods to sandwich the tendons 54 therebetween as illustrated in FIGURE 7 with the rods 58 crossing each other as at 62 and 64 along the upper and lowermost corners of the framework on both sides of the longitudinal center line thereof. However, only one set of mild reinforcing rods 58 may be utilized if desired.

After the frame and the reinforcing tendons and rods 54 and 58 have been erected to complete the framework of the hull 10, any suitable inner and outer open-ended mold surface means are erected in a manner sandwiching the framework therebetween in spaced relation thereto and with the steel tendons 54 projecting outwardly from the opposite ends of the inner and outer mold surface means.

If it is desired, the steel tendons 54 may be erected any time before or even after the inner and outer mold surface means are erected and placed under tension any time after their erection before the next step of pouring hardening fluent such as any suitable cementitious material between the inner and outer mold surface means, during which pouring step the prestressed steel tendons are retained in a tensioned condition. Thereafter, the hardening fluent may be allowed to thoroughly harden after which the steel tendons may be relieved of their tension so as to place the hardened fluent in compression and then the mold surface means may be removed. However, the steps of relieving the tendons of their tension and removing of the inner and outer mold surface means may be carried out with either step preceding the other and in fact the inner and outer mold surface means of the center section 12 of the hull 10 may be delayed until after the bow and stern sections 14 and 16 are erected.

In order to form the bow and stern sections 14 and 16, the extended ends of the steel tendons 54 are bent as illustrated in FIGURE 8 of the drawings so as to conform to the desired shape of the completed bow and stern sections 14 and 16 and so as to overlap each other at the terminal ends of the hull construction as at 66 and 70. Thereafter, suitable mild steel reinforcing rods 72 and 74 may be erected as illustrated in FIGURE 8 of the drawings to complete the skeleton frameworks of the bow and stern sections 14 and 16. Thereafter the end faces of the hardened and prestressed cementitious skin 76 of the center section 12 may have a bonding epoxy applied thereto.

Either before or after the extended ends of the steel tendons 54 are bent as illustrated in FIGURE 8 of the drawings any suitable mold surface means may be erected at the bow and stern ends of the hull 10. In addition, after the bending of the steel tendons 54 as illustrated in FIG- URE 8 and either before or after the end faces of the cementitious skin 76 have bonding epoxy applied thereto, the bow and stern outer mold forming means may be erected with the inner and outer mold forming means of the bow and stern sections 14 and 16 also disposed in spaced embracing relationship to the skeleton framework of the bow and stern sections 14 and 16 defined by the bent extended end portions of the tendons 54 and the reinforcing rods or members 72. Thereafter any suitable hardening fluent may be poured between the inner and outer mold forming means of the bow and stern sections 14 and 16 so as to define the cementitious skin portions 78 and 80, respectively, thereof. After the hardening fluent uti lized to form skin portions 78 and 89 has thoroughly hardened, the bow and stem inner and outer mold means may be removed and suitable bulkhead or partition defining assemblies such as those indicated at 3% may be erected within the hull construction 10.

In forming the hull construction the rib sections 28 and the longitudinal and transverse reinforcing rods (not shown) may be first erected. Then, the inner and outer mold form means of the center section may be erected prior to pouring the hardening fluent therebetween. However, the transverse reinforcing rods of the hull construction 10 corresponding to the rods 58 may extend completely about the girth thereof and may in fact be formed of one continuous reinforcing rod if desired inasmuch as the hull construction 19 is of the closed deck-type. Accordingly, it may be seen that the hull construction may be formed by the same steps which are utilized in the construction of the hull 10 except that the inner surface mold means are removed through hatch openings (not shown) after the cementitious skin 84 of the center section of the hull 10' has hardened. Of course, suitable bow and stern sections may be erected and secured to the center section of the hull construction 18 in a manner similar to that in which the bow and stern sections 14 and 16 are constructed.

The steel tendons 54 and the reinforcing rods 58 are preferably anchored to the rib sections 28 and also the keelsons 42 in any convenient manner at points spaced longitudinally along the tendons 54 of the rods 58. Further, the keelsons 42 and the longitudinally extending frame deck members may be eliminated if desired. Still further, if the beam of the hull construction 19 is not too great, the frame-like rib sections 28 may also be eliminated thereby relying on only the skin 76 having the tensioned tendons 54 embedded therein for forming the hull construction 10.

If it is desired, the keelsons 42 may be constructed integrally with the skin 76 and of reinforced concrete. Still further, it will be noted that the bulkhead or partition defining assemblies 30 are not necessarily secured to all of the transversely extending frame-like rib sections and that there may be one or more rib sections 28 disposed between adjacent bulkhead assemblies 30. Finally, by pretensioning the tendons 54 and utilizing mild steel in the construction of the reinforcing rod 58 as the tendons 54 are relieved of their tension after the skin 76 has hardened, the pretensioned tendons 54 will slightly longitudinally compress the skin 76 and thus cause it to expand slightly in thickness, which expansion will cause the reinforcing rods 58 to be post-tensioned.

As hereinbefore set forth, inasmuch as the tendons 54 are straight they can be more readily tensioned and tensioned to a greater degree. If the sides or bottom of the center section 12 were of configurations necessitating that the tendons 54 would have to be tensioned while in a curved or other than straight condition, considerable extra forms and braces would have to be utilized to maintain such curved tendons under tension during the pouring and hardening of the cementitious material of which the skin 76 is constructed. Therefore, the hull 19 of the instant invention is constructed in three sections with the center section extending throughout a major portion of he length of the hull and including straight bottom and side portions thereby enabling these portions to have straight and highly tensioned tendons embedded therein. After the center section 12 is constructed, then the relatively short and reinforced bow and stern sections 14 and 16 are applied to the opposite ends of the center section .12. Inasmuch as the stresses on the hull 10 are greatest in the center portion of the center section 12 and only minimal in the bow and stern sections 14 and 16, the untensioned reinforcement of the bow and stern sections 14 and 16 does not effect the over-all strength of the hull 10.

If it is desired, the rib frame sections 28 may also be constructed of reinforced concrete as opposed to steel structural members and suitable framing ribs, either constructed of steel or reinforced concrete and similar to the rib sections 28 may be utilized in the bow and stern sections 14 and 16. Further, the rib sections 23 can of course also be constructed of reinforced concrete and it is to be noted that the mild steel rods 58, 72 and 74 may be constructed of similar material.

It it is desired, suitable end bulk heads (not shown) may be secured to the opposite ends of the center section 12 and prefabricated bow and stern sections, replacing the sections 14 and 16 may be secured to the opposite ends of the center section 12 after it has been complete If such prefabricated bow and stern sections are utilized, they may be attached to the center section 12 in any convenient manner which would enable them to be replaced without any undue modifications to the center section 12. It is of course also to be noted that the cementitious material of which the skin 76 is constructed may be vibrated in order that it may be compacted as the cementitious material is being poured. Further, should the apparatus by which the cementitious material is being poured be unable to complete the pouring operation of the center section .12 before the first poured portion begins to set, and it becomes necessary to pour the skin 76 in more than one operation, any suitable bonding compound may be utilized on the cold joints between old and freshly poured portions of the skin 7 6.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. A prestressed hull center section, said center section including a frame having a plurality of longitudinally spaced and transversely extending upright rib sections, a skin of hardened fluent material interconnecting corresponding portions of said rib sections and disposed at least partially outwardly of said rib sections, said sk'm having circumferentially spaced and longitudinally extending pretensioned steel tendons embedded therein, said tendons projecting outwardly of the opposite ends of said center sections and terminating in overlapping relationship with closed bow and stern sect-ions defining untensioned skeleton frames which receive cementitious skin sections thereby closing the bow and stern end of said center section, having said skeleton frames embedded therein, and forming continuations of corresponding por- 'tions of said center section.

2. The combination of claim 1 wherein said center section includes circumferentially extending and longitudinally spaced post tensioned mild steel reinforcing rods extending about the girth of said center sect-ion and also embedded in said skin.

3. The combination of claim 2 wherein said center section frame includes a plurality of longitudinally spaced and transversely extending upright open frame-like rib sect-ions and at least a pair of lower transversely spaced longitudinally extending keelsons disposed on opposite sides of the longitudinal center line of said center section and spaced inwardly from the opposite sides thereof interconnecting corresponding portions of said rib sections, said keelsons also being enclosed by said skin, said center section also including an integral upper deck portion extending inwardly from the side portion of the center References Cited UNITED STATES PATENTS 3/1944 Upson et al. l14-65 8/1947 Billing ll4--65 MILTON BUCHLER, Primary Examiner.

A. H. FARRELL, Assistant Examiner. 

1. A PRESTRESSED HULL CENTER SECTION, SAID CENTER SECTION INCLUDING A FRAME HAVING A PLURALITY OF LONGITUDINALLY SPACED AND TRANSVERSELY EXTENDING UPRIGHT RIB SECTIONS, A SKIN OF HARDENED FLUENT MATERIAL INTERCONNECTING CORRESPONDING PORTIONS OF SAID RIB SECTIONS AND DISPOSED AT LEAST PARTIALLY OUTWARDLY OF SAID RIB SECTIONS, SAID SKIN HAVING CIRCUMFERENTIALLY SPACED AND LONGITUDINALLY EXTENDING PRETENSIONED STEEL TENDONS EMBEDDED THEREIN, SAID TENDONS PROJECTING OUTWARDLY OF THE OPPOSITE ENDS OF SAID CENTER SECTIONS AND TERMINATING IN OVERLAPPING RELATIONSHIP WITH CLOSED BOW AND STERN SECTIONS DEFINING UNTENSIONED SKELETON FRAMES WHICH RECEIVE CEMENTITIOUS SKIN SECTIONS THEREBY CLOSING THE BOW AND STERN ENDS OF SAID CENTER SECTION, HAVING SAID SKELETON FRAMES EMBEDDED THEREIN, AND FORMING CONTINUATIONS OF CORRESPONDING PORTIONS OF SAID CENTER SECTION. 